Method of electrically treating metal



Patented Dec. 23, 1941 Robert F. Renkin, Sharon, Pa., asslgnor of onehalf to Henry A. Boomer, Pittsburgh, Pa...

' No Drawing;

Application January 23, 1940; Serial N0. 315,186

7 Claims. (Cl. 205-21) The invention relates'generally to the cleaning of metal products, and more particularly to the cleaning or cleaning and coating of metal products with a relatively soft'metal'.

In the manufacture of relatively small gauge metal products, such as sheets, stripsheets, strips and Wire, a number of successive reductions by rolling'or drawing operations 'is required before the metal product is'brought' down to the desired gauge or thickness. -Such cold working or re-' ducing operations greatly diminish the ductility and workability of the metal product, so that at frequent intervals during the reducing operations the metal product must be subjected to annealing treatments to restore its ductility, followed by the usualacid pickling to remove any scale.

In making small gauge wire, after the wire has gauge and annealed, the stainless steel wire must the wire becomes so brittle as to require further annealing; The stainless steel wire is then passed through an acid wash to remove the remaining lead coating, and is again annealed, pickled,-

other series of drawing operations. I

After the wire has been drawndownto say 12 fiuxed, and lead coated in preparation, for anbe given another etching pickle-treatment, prefbeen drawn down to say 12 gauge by the prelimine ary drawing operations, it is in the form of ex-, tremely long stra'nds'so that in order to be handled economically and efiiciently it is pickled, fluxed, and coated in coils prior to the last series of drawing operations.

However, when coils having many turns of wire are dipped in' a pickling and then in a coating bath, it isan expensive and messy procedure,

and. where the wire is required to be coated with arelatively soft 'metal, it is.very diflicult if'not impossible to obtain a uniform and adherent coating, because the turns of wire stick together in many places with 'the result that an uneven, coating is produced. I Where steel having a very low carbon content is galvanized, as for example steel telephone wire, by passing the wire from the pickling bath into the spelter pot, the galvanized coating is notsufficiently ductile or adherent to meet certain tests required of such wire, and one method of satisfactorily galvanizing such wire is fully set forth in my copending application Serial No. 309,224, filed December I4, .1939, and entitled Method of coating metal. Such method includes subjecting the wire to a dry pickling treatment, then passing it through a special fluxingbath, and passing it into the galvanizing bath.

In the manufacture of certain metal products,

as for example, stainless steel wire, it has been found expedient to coat the wire with a soft metal such as lead prior to the drawing operations, the lead acting as a lubricant durin the erably in hydrochloric acid, to produce an etchedsurface on the wire before a lead coating can be made to adhere thereto sufliciently to act as a lubricant during subsequent drawing operations This etching pickle treatment causes a substantial loss of metal. In making stainless steel wire according to conventional practice, it has been found that not only are the etchingand lead coating steps expensive, but the lead coating ebtainable is uneven and non adherent tothe'extent that a minimum number of-subsequent drawing operations can be made on the wire. For example, with stainless steelwire of the order of 123 gauge, .099" diameter, it has not been possible with conventional practice to perform more j I than three reductions, bringing the wire-down to' about .050" diameter,-without reannealing.

I have discovered thatfthe usual acid pickling treatment can be eliminated by passing themetal product, after. an annealing treatment, through an electrolyzed flux wherein the metal product made-the anode, and that the metal product can then be passed directly into the metal coating bath to obtain a uniform and very adherent coating. I A r In applying thisdiscovery and invention to the making of stainless steel wire, even though the wire may be semi-oxidized or bright annealed after the preliminary drawing operations, I have found that'by' passing the wire through, an elec- I trolyzed flux and making the wire the anode, the etching pickle step required in conventional practice can be eliminated and the wire passed drawing operations. Presentfpractice in' making stainlesssteel wire preferably includes passing hot rolled stainless steel rods-through an acid etchingpickle, fluxin lead coating, and;then V f drawing-the wire down as faras possible or until provid a novel method of producing a uniform directly from the flux into a molten lead bath to produce a uniform lead coating thereon.

Moreover, stainless steel wire made according to my novel method is' capable of being reduced by an increased number of successive drawing operations, without reannealing, to produce a very small gauge wire product.

It isa, generalobject of the present invention to provide a novel method of cleaning metal products by electrically treating, the same.

A specific object of the present invention is'to number of drawing operations can be performed without annealing.

A still further object is to provide a novel method of cleaning and coating metal, which method produces an improved product with a minimum amount of handling and at a minimum cost.

These objects, together with others which will appear from the following detailed. description of the invention, are accomplished by the method steps, and the combinations and sub-combinations thereof, which are hereinafter set forth in detail and defined in the appended claims.

By way of example, the invention will be described herein as applied to the manufacture of steel wire, but it is to be understood that, within the scope of the appended claims, the invention is applicable to the making of other ordinary steel products, such as sheets, strips, stripsheets, etc.; as well as to the manufacture of similar products of other metals. 7

In carrying out my novel method in the manufacture of small gauge stainless steel wire, I start with wire which preferably has been drawn down or reduced to some extent according to conventional practice. This'preliminary reducing treatment may include pickling hot rolled stainless steel rods, fiuxing and lead coating them, and then subjecting them to successive drawing operations, between which additional annealing, fluxing and pickling steps are interposed as and when required.

After the stainless steel wire has been thus reduced to say about 1201' 12 ,42 gauge, it is coiled and annealed but not pickled before treating it according to my novel method. The gauge of the wire upon which I begin my novel treatment may vary according to the capacity of the equipment being used, and I mention 12 or 12 gauge merely as an example.

The wire coils to be treated by my novel method may have been annealed so as to. produce an oxidized or semi-oxidized surface on the wire, or they may have been bright annealed in an inert atmosphere such as ammonia gas. The wire is first passed through a separate fluxing bath of more or less ordinary composition, preferably'by placing the coils on suitable pay oif reels and feeding the wire strands continuously through the fluxing bath.

I prefer to use a flux solution having the following composition, although the composition of the flux may be varied considerably and still give satisfactory results.

, Parts Zinc chloride (liquid) (by volume) 1 Zinc ammonium chloride (crystals) 2 Sal ammoniac 1 Water 1 which gives a very saturated solution having a Baum reading of about 45, operating at 175- 200 F.

A very-important feature of the invention is that the flux is constantly electrolyzed with the wire acting as the anode and preferably the flux tank acting as the cathode. This may be done by connecting the positive terminal from a power source to one of the usual wire holddown rolls immersed in the flux, thu making the wire the anode, and by connecting the other terminal from the power source to a convenient place on the flux tank wall, thus making the tank the cathode.

The amount of current and fluxing time required will vary according to the size of the apparatus used and the various operating conditions. but I have successfully treated 12 gauge stainless steel wire using a direct current of 7 /2 to 15 volts with 20 to 40 amperes, and immersing the wire in the flux from 5 to 10 seconds.

From the fluxing bath, the wire is led directly into and through a separate bath of molten lead formed of ordinary or commercial lead maintained at approximately 620 to 670 F., after which the wire is ready for further drawing operations.

The reaction of the electrolyzed flux using the wire as the anode is difficult to explain, but apparently a cleaning or deplating of the wire surmolten commercial lead, a very uniform adherent lead coating is obtained on the wire.

In cleaning and coating 12 /2 gauge, .099" diameter stainless steel wire according to this method, I have been able to then pass the wire through five successive drawing operations without reannealing, to satisfactorily produce wire of .037" diameter.

The step by step reductions for these five draw-.

ing steps were as follows:

First draw .099" to .082" Second draw .082" to .069" Third draw .069"to .053" Fourth draw .053" to .044" Fifth draw .044" to .037"

With prior conventional practice wherein 12 gauge stainless steel wire was annealed, pickled in acid, fluxed, and then lead coated, great difficulty was experienced in obtaining a lead coating which was sufficiently adherent, and it was practically impossible to produce a uniform lead coating,-with thev result that the coated wire could not be given more than three draws, reducing it to about .050 diameter before reannealing.

Accordingly, my invention provides a novel and improved method of cleaning and coating stainless steel wire without the usual pickling, making possible an increased numberof drawing operations to produce wire of smaller gaugesthan has heretofore been possible, without reannealing.

When it is desired to galvanize metal products on which it is difllcult to obtain a uniform and adherent coating, as for example low carbon steel telephone wire, the wire can be taken from the annealing furnace, or from the dry pickling furnace described in my copending application Serial No. 309,224, and passed through the electrolyzed flux containing preferably zinc chloride,

zinc ammonium chloride and sal ammoniac as set ciently ductile and adherent a withstand the 2. In a method of cleaning and coating'steel, the steps of passing the steel through a separate flux solution containing zinc chloride electrolyzed by passing electric current through the flux with the steel acting as the anode, and then passing the steel directly into a separate molten lead coating bath.

3. A methodof cleaning and coating stainless steel which includes annealing the steel, passing the steel through a separate flux solution containing zinc chloride electrolyzed by passing electric current through the flux with the steel acting as the anode, and then passing the steel directly into a separate-bath or molten commercial lead.

4. A method of cleaning and coating stainless steel wire for cold drawing, which includes annealing the wire, passing, the steel through a separate flux solution containing zinc chloride, zinc ammonium chloride and sal ammoniac, electrolyzlng the flux during the passage of-the wire therethrough by passing an electric current through the flux with the wire acting as the anode, and then passing the wire directly into a separate bath of molten lead. 1

5. In a method of treating metal, the steps of annealing the metal, and then cleaning and fluxing the metal by moving the metal through aseparate flux solution containing zinc chloride,

. zinc ammonium chloride and sal ammoniac, and

electrolyzing the flux during the passage of the metal therethrough by passing an electric current through the flux with the metal acting as the anode.

6. A method of reducing stainless steel wire which includes annealing the wire, passing the wire through a separate flux solution containing zinc chloride, electrolyzing the flux during the passage of the wire therethrough by passing an electric current through the flux with the wire acting as the anode, then passing the wire through a separate bath of molten lead, and then subjecting the wire to successive drawing operationsto to per cent reduction, without reannealing the wire.

7. A method of reducing metal which includes annealing the metal, passing the metal through a separate flux solutioncontaining zinc chloride, electrolyzing the flux during the passage of the metal therethrough by passing an electric current through the flux with the metal acting as the anode, then passing the metal through a separate molten lead coating bath, and then subjecting the metal to successive cold working operations.

ROBERT F. RENKIN. 

